NAME

       LWP::Protocol::PSGI - Override LWP's HTTP/HTTPS backend with your own PSGI application

SYNOPSIS

         use LWP::UserAgent;
         use LWP::Protocol::PSGI;

         # $app can be any PSGI application: Mojolicious, Catalyst or your own
         my $app = do {
             use Dancer;
             set apphandler => 'PSGI';
             get '/search' => sub {
                 return 'searching for ' . params->{q};
             };
             dance;
         };

         # Register the $app to handle all LWP requests
         LWP::Protocol::PSGI->register($app);

         # can hijack any code or module that uses LWP::UserAgent underneath, with no changes
         my $ua  = LWP::UserAgent->new;
         my $res = $ua->get("http://www.google.com/search?q=bar");
         print $res->content; # "searching for bar"

         # Only hijacks specific host (and port)
         LWP::Protocol::PSGI->register($psgi_app, host => 'localhost:3000');

         my $ua = LWP::UserAgent->new;
         $ua->get("http://localhost:3000/app"); # this routes $app
         $ua->get("http://google.com/api");     # this doesn't - handled with actual HTTP requests

DESCRIPTION

       LWP::Protocol::PSGI is a module to hijack any code that uses LWP::UserAgent underneath
       such that any HTTP or HTTPS requests can be routed to your own PSGI application.

       Because it works with any code that uses LWP, you can override various WWW::*, Net::* or
       WebService::* modules such as WWW::Mechanize, without modifying the calling code or its
       internals.

         use WWW::Mechanize;
         use LWP::Protocol::PSGI;

         LWP::Protocol::PSGI->register($my_psgi_app);

         my $mech = WWW::Mechanize->new;
         $mech->get("http://amazon.com/"); # $my_psgi_app runs

TESTING

       This module is extremely handy if you have tests that run HTTP requests against your
       application and want them to work with both internal and external instances.

         # in your .t file
         use Test::More;
         use LWP::UserAgent;

         unless ($ENV{TEST_LIVE}) {
             require LWP::Protocol::PSGI;
             my $app = Plack::Util::load_psgi("app.psgi");
             LWP::Protocol::PSGI->register($app);
         }

         my $ua = LWP::UserAgent->new;
         my $res = $ua->get("http://myapp.example.com/");
         is $res->code, 200;
         like $res->content, qr/Hello/;

       This test script will by default route all HTTP requests to your own PSGI app defined in
       $app, but with the environment variable "TEST_LIVE" set, runs the requests against the
       live server.

       You can also combine Plack::App::Proxy with LWP::Protocol::PSGI to route all requests made
       in your test against a specific server.

         use LWP::Protocol::PSGI;
         use Plack::App::Proxy;

         my $app = Plack::App::Proxy->new(remote => "http://testapp.local:3000")->to_app;
         LWP::Protocol::PSGI->register($app);

         my $ua = LWP::UserAgent->new;
         my $res = $ua->request("http://testapp.com"); # this hits testapp.local:3000

METHODS

       register
             LWP::Protocol::PSGI->register($app, %options);
             my $guard = LWP::Protocol::PSGI->register($app, %options);

           Registers an override hook to hijack HTTP requests. If called in a non-void context,
           returns a guard object that automatically resets the override when it goes out of
           context.

             {
                 my $guard = LWP::Protocol::PSGI->register($app);
                 # hijack the code using LWP with $app
             }

             # now LWP uses the original HTTP implementations

           When %options is specified, the option limits which URL and hosts this handler
           overrides. You can either pass "host" or "uri" to match requests, and if it doesn't
           match, the handler falls back to the original LWP HTTP protocol implementor.

             LWP::Protocol::PSGI->register($app, host => 'www.google.com');
             LWP::Protocol::PSGI->register($app, host => qr/\.google\.com$/);
             LWP::Protocol::PSGI->register($app, uri => sub { my $uri = shift; ... });

           The options can take either a string, where it does a complete match, a regular
           expression or a subroutine reference that returns boolean given the value of "host"
           (only the hostname) or "uri" (the whole URI, including query parameters).

       unregister
             LWP::Protocol::PSGI->unregister;

           Resets all the overrides for LWP. If you use the guard interface described above, it
           will be automatically called for you.

DIFFERENCES WITH OTHER MODULES

   Mock vs Protocol handlers
       There are similar modules on CPAN that allows you to emulate LWP requests and responses.
       Most of them are implemented as a mock library, which means it doesn't go through the LWP
       guts and just gives you a wrapper for receiving HTTP::Request and returning HTTP::Response
       back.

       LWP::Protocol::PSGI is implemented as an LWP protocol handler and it allows you to use
       most of the LWP extensions to add capabilities such as manipulating headers and parsing
       cookies.

   Test::LWP::UserAgent
       Test::LWP::UserAgent has the similar concept of overriding LWP request method with
       particular PSGI applications. It has more features and options such as passing through the
       requests to the native LWP handler, while LWP::Protocol::PSGI only allows one to map
       certain hosts and ports.

       Test::LWP::UserAgent requires you to change the instantiation of UserAgent from
       "LWP::UserAgent->new" to "Test::LWP::UserAgent->new" somehow and it's your responsibility
       to do so. This mechanism gives you more control which requests should go through the PSGI
       app, and it might not be difficult if the creation is done in one place in your code base.
       However it might be hard or even impossible when you are dealing with third party modules
       that calls LWP::UserAgent inside.

       LWP::Protocol::PSGI affects the LWP calling code more globally, while having an option to
       enable it only in a specific block, thus there's no need to change the UserAgent object
       manually, whether it is in your code or CPAN modules.

AUTHOR

       Tatsuhiko Miyagawa <miyagawa@bulknews.net>

COPYRIGHT

       Copyright 2011- Tatsuhiko Miyagawa

LICENSE

       This library is free software; you can redistribute it and/or modify it under the same
       terms as Perl itself.

SEE ALSO

       Plack::Client LWP::UserAgent